The present invention relates to polymers and co-polymers based on vinyl cyclohexane (VCH) with predominantly syndiotactic configuration and a process for their manufacture and their use as optical material. The materials may be processed into moulded bodies by extrusion or injection moulding and are particularly suitable as substrate for optical data storage media such as compact discs, video discs, re-writable optical discs.
Transparent plastics such as aromatic polycarbonate, polymethyl methacrylate or polystyrene may be used as substrate for optical data storage media. Addition co-polymers comprising ethylene and a norbornene derivative or a tetracyclododecene derivative and hydrogenated products of ring-opened metathesis polymers comprising norbornene or tetracyclododecene are also considered.
None of the current substrate materials may, however, be used without restriction for very high data storage densities ( greater than 5, particularly  greater than 10 Gbytes related to a disc of 120 mm diameter). Very low birefringence and water absorption, high heat deflection temperature, accompanied by adequate mechanical properties and low melting viscosity, are simultaneously required for this purpose.
Although aromatic polycarbonates have very good mechanical properties and heat deflection temperature, their birefringence and water absorption are too high.
The birefringence of polystyrene is too high and its heat deflection temperature too low.
The water absorption of polymethyl methacrylate is too high and its dimensional stability too low. The birefringence of addition co-polymers comprising ethylene and a non-polar norbornene or tetracyclododecene is low and they have virtually no water absorption.
These materials are very expensive to produce, however. The materials may only be produced in optically pure quality with great difficulty. The presence of gel contents also reduces their applications as optical materials. Considerable technical outlay is involved in separating the catalysts and co-catalysts.
Optical materials comprising a hydrogenation product of a polymer comprising an alkenyl-aromatic hydrocarbon compound or a co-polymer thereof are described in GB 933,596 (=DE-AS 1 131 885), EP-A 317 263, U.S. Pat. Nos. 4,911,966 and 5,178,926. There is no reference to the configuration.
Hermann Staudinger was the first to describe the hydrogenation of polystyrene in 1929. More recent patent literature concerns the basic micro-structure of polyvinyl cyclohexane and/or hydrogenated polystyrene. The prior art is that amorphous vinyl cyclohexane polymers have an atactic configuration and crystalline VCH (vinyl cyclohexane) polymers either isotactic or syndiotactic configuration (EP-A 0 322 731, EP-A 0 423 100, U.S. Pat. Nos. 5,654,253; 5,612,422; WO 96/34896). Isotactic PVCH (polyvinyl cyclohexane) is produced in the presence of Ziegler catalysts and has a high melting point (J. Polym. Sci., A2, 5029 (1964). EP-A 0 322 731 describes that vinyl cyclohexane polymers with syndiotactic configuration by hydrogenation of syndiotactic polystyrene are crystalline, wherein the quantity of the diads is at least 75% and the quantity of the pentads at least 30%. WO 94/21694 describes a process for producing hydrogenated poly(alkenyl-aromatic) polymers and poly(alkenyl-aromatic)/polydiene block co-polymers. Syndiotactic polystyrene is mentioned in general terms.
Processes which lead to isotactic, syndiotactic and atactic hydrogenated polystyrene which have the material properties known hitherto are described in WO 94/21694, U.S. Pat. No. 5,352,744, wherein specific catalysts are used. Processes for the hydrogenation of atactic polystyrene to produce atactic hydrogenated polystyrene by the use of specific catalysts are described in U.S. Pat. Nos. 5,654,253; 5,612,422; WO 96/34896.
Atactic polymers are regular polymers. By definition they have the possible configurative base units in equal quantities, with ideal-random distribution from molecule to molecule (TUPAC). They are distinguished by the same number of iso-and syndiotactic diads. An amorphous material with only one glass stage with no crystalline content is described.
The present invention provides a polymer or co-polymer based on vinyl cyclohexane, wherein olefins, acrylic acid derivatives, maleic acid derivatives, vinyl ethers or vinyl esters may be used in production as co-monomers, with syndiotactic configuration, characterized in that the quantity of diads is greater than 50.1% and less than 74%. The polymers based on vinyl cyclohexane are amorphous polymers.
The polymers according to the invention are distinguished by, high transparency, low birefringence and high heat deflection temperature and may therefore be used as substrate material for optical data storage media. Because of its crystallinity the known, isotactic PVCH is unsuitable for optical applications.
The invention provides hydrogenated products of polystyrene which lead to an amorphous hydrogenated polystyrene with an excess of the racemic (syndiotactic) diads.
The vinyl cyclohexane polymer of this invention is a new amorphous polymer with a defined stereostructure which is distinguished by the predominant occurrence of the racemic diads configuration and may be efficiently produced by the process described.
A polymer based on vinyl cyclohexane is preferred with the repeating structural unit of formula (I) 
in which
R1 and R2 independently of each other stand for hydrogen or C1-C6 alkyl, preferably C1-C4 alkyl, and
R3 and R4 independently of each other stand for hydrogen or for C1-C6 alkyl, preferably C1-C4 alkyl, particularly methyl and/or ethyl, or R3 and R4 jointly stand for alkylene, preferably C3 or C4 alkylene (fused 5 or 6-membered cycloaliphatic ring),
R5 stands for hydrogen or C1-C6 alkyl, preferably C1-C4 alkyl,
R1, R2 and R5 independently of each other stand in particular for hydrogen or methyl.
Apart from the stereoregular head-to-tail linkage, the linkage may have a small content of head-to-head linkage. The amorphous, predominantly syndiotactic polymer based on vinyl cyclohexane may be branched via centres and may have a stellar structure for example.
The following may preferably be used in the polymerization of the starting polymer (optionally substituted polystyrene) and be co-incorporated into the polymer as co-monomers: olefins with in general 2 to 10 C atoms, such as for example ethylene, propylene, isoprene, isobutylene, butadiene, C1-C8, preferably C1-C4 alkyl esters of acrylic and/or methacrylic acid, unsaturated cycloaliphatic hydrocarbons, e.g. cyclopentadiene, cyclohexene, cyclohexadiene, optionally substituted norbornene, dicyclopentadiene, dihydrocyclopentadiene, optionally substituted tetracyclododecenes, nucleus-alkylated styrenes, xcex1-methylstyrene, divinyl benzene, vinyl esters, vinyl acids, vinyl ethers, vinyl acetate, vinyl cyanides such as for example acrylonitrile, methacrylonitrile, maleic anhydride and mixtures of these monomers.
The amorphous vinyl cyclohexane polymer according to the invention has a syndiotactic diad content, determined by two-dimensional NMR spectroscopy, of 50.1 to 74%, preferably of 52-70%. Methods for microstructure elucidation using 13C-1H correlation spectroscopy of the methylene carbon atoms of a polymer backbone are generally known and are described by A. M. P. Ros and O. Sudmeijer for example (A. M. P. Ros, O. Sudmeijer, Int. J. Polym. Anal. Charakt. (1997) 4, 39).
The signals of crystalline isotactic and syndiotactic polyvinyl cyclohexane are determined by means of two-dimensional NMR spectroscopy. The methylene-carbon atom (in the polymer backbone) of the isotactic polyvinyl cyclohexane splits into two separated proton signals in the 2-D CH correlation spectrum and exhibits the pure isotactic diad configuration. In contrast, for the carbon atom C 1, syndiotactic polyvinyl cyclohexane exhibits only one signal in the 2-D CH correlation spectrum. The amorphous syndiotactically rich polyvinyl cyclohexane according to the invention has an integral intensity excess of the syndiotactic diads compared to the isotactic diad configuration.
The birefringence determined on these materials, measured with the aid of the rheo-optical constant CR, isxe2x88x920.3 GPaxe2x88x921, which is more than one power of ten lower than that for polycarbonate (CR=+5.4 GPaxe2x88x921). The method for measuring the rheo-optical constant is described in EP-A 0621 297. The plane-parallel 150 to 1000 xcexcm sample bodies required for this may be produced by melt compression moulding or film casting. Compared with polycarbonate the material may be regarded as birefringence-free. It has a high heat deflection temperature, low water absorption, accompanied by adequate mechanical properties, and is therefore an ideal material for very high optical data storage densities ( greater than 10 Gbytes on a disc of 120 mm diameter).
In general the vinyl cyclohexane (co)polymers have absolute molecular weights Mw weight average of 1000-10000000, preferably of 60000-1000000, most particularly preferably 70000-600000, determined by light scatter.
In general the homopolymers based on vinyl cyclohexane according to the invention have a glass temperature  greater than 140xc2x0 C., preferably  greater than 145xc2x0 C., determined by DSC.
The co-polymers may be present both randomly and as block co-polymers.
The polymers may have a linear chain structure and also have branch points by co-units (e.g. graft co-polymers). The branch centres contain stellar or branched polymers for example. The polymers according to the invention may have other geometrical shapes of the primary, secondary, tertiary, optionally quaternary polymer structure; helix, double helix, pleated sheet etc. and/or mixtures of these structures may be mentioned.
Block co-polymers contain di-blocks, tri-blocks, multi-blocks and stellar block co-polymers.
The VCH (co)polymers are produced by polymerizing derivatives of styrene with the corresponding monomers radically, anionically, cationically or by metal complex initiators and/or catalysts and then partially or completely hydrogenating the unsaturated aromatic bonds (cf WO94/21694, EP A 322 731 for example). They are distinguished by the predominant occurrence of the syndiotactic configuration of the vinyl cyclohexane units of the present invention.
The VCH (co)polymers may be further produced, for example, by hydrogenation of aromatic polystyrenes and/or their derivatives in the presence of a catalyst, wherein an ether which has no xcex1-hydrogen atom on a carbon atom adjacent to the ether function, or a mixture of such ethers or a mixture of at least one of the said ethers with solvents suitable for hydrogenation reactions is used as solvent.
The reaction is generally conducted at volume concentrations of the ether component with respect to the entire solvent of 0.1% to 100%, preferably 1% to 60%, most particularly preferably 5% to 50%. The ether component may be designated as a co-catalyst.
In general the process leads to a virtually complete hydrogenation of the aromatic units. Usually the degree of hydrogenation is xe2x89xa780%, preferably xe2x89xa790%, most particularly preferably xe2x89xa799%, particularly 99.5 to 100%. The degree of hydrogenation may be determined by NMR or UV spectroscopy for example.
The starting polymers are generally known (WO 94/21 694 for example).
Ethers of formula (I): 
in which
R1, R2, R3 and R4 independently of each other stand for C1-C8 alkyl, which is straight-chain or branched, or for C5-C6 cycloalkyl optionally substituted by C1-C4 alkyl or
two of the groups R1, R2, R3 and R4 form a ring with 3 to 8, preferably 5 or 6 carbon atoms,
are preferably used as solvent.
Methyl-t-butyl ether, ethyl-t-butyl ether, propyl-t-butyl ether, butyl-t-butyl ether, methyl-(2-methyl-2-butyl)ether, (tert. amyl-methyl ether), 2-ethoxy-2-methylbutane (ethyl-tert.-amyl ether) are particularly preferred.
The quantity of catalyst used depends on the process conducted; this may be continuous, semi-continuous or discontinuous.
The ratio of catalyst to polymer is generally 0.3-0.001, prefer ably 0.2-0.005, particularly preferably 0.15-0.01, for example, in the discontinuous process.
The polymer concentrations, related to the overall weight of solvent and polymer, are generally 80 to 1, preferably 50 to 10, particularly 40 to 15 wt. %.
The starting polymers are hydrogenated according to generally known methods (WO 94/21 694, WO 96/34 895, EP-A-322 731 for example). A plurality of known hydrogenation catalysts may be used as catalysts. Preferred metal catalysts are quoted in WO 94/21 694 or WO 96/34 896 for example. Any catalyst known, for hydrogenation reactions may be used as catalyst. Suitable catalysts are ones with a large surface (such as 100-600 m2/g) and small average pore diameter (20-500xc3x85 for example). Catalysts with a small surface (such as xe2x89xa710 m2/g) and large average pore diameters, which are characterized in that 98% of the pore volume have pores with pore diameters greater than 600xc3x85 (approx. 1000-4000xc3x85 for example) (cf. U.S. Pat. Nos. 5,654,253, 5,612,422, JP-A 03076706 for example) are also suitable. Raney nickel, nickel on silicon dioxide or silicon dioxide/aluminium oxide, nickel on carbon as carrier and/or precious metal catalysts such as Pt, Ru, Rh, Pd are used in particular.
The reaction is generally carried out at temperatures between 0 and 500xc2x0 C., preferably between 20 and 250xc2x0 C., particularly between 60 and 200xc2x0 C.
The solvents which may conventionally be used for hydrogenation reactions are described in DE-AS 1 131 885 for example (see above).
The reaction is generally carried out at pressures of 1 bar to 1000 bar, preferably 20 to 300 bar, particularly 40 to 200 bar.
The polymers or copolymers based on vinyl cyclohexane according to the invention are outstandingly suitable for producing optical data storage media, preferably with data storage densities  greater than 5, particularly  greater than 10 Gbytes, related to a disc of 120 mm diameter.
The following may be quoted as examples of optical data storage media:
Magneto-optic disc (MO-disc)
Mini-disc (MD)
ASMO (MO-7) (xe2x80x9cAdvanced storage magnetoopticxe2x80x9d)
DVR (12 Gbyte Disc)
MAMMOS (xe2x80x9cMagnetic Amplifying magneto optical systemxe2x80x9d)
SIL and MSR (xe2x80x9cSolid immersion lensxe2x80x9d and xe2x80x9cmagnetic superresolutionxe2x80x9d)
CD-ROM (Read only memory)
CD, CD-R (recordable), CD-RW (rewritable), CD-I (interactive), Photo-CD
Super Audio CD
DVD, DVD-R (recordable), DVD-RAM (random access memory); DVD 32 digital versatile disc
DVD-RW (rewritable)
PC+RW (Phase change and rewritable)
MMVF (multimedia video file system)
Because of their outstanding optical properties the polymers according to the invention are also particularly suitable for producing optical materials, e.g. for lenses, prisms, mirrors, colour filters etc. Also as media for holographic reproductions (e.g. cheque, credit cards, identity cards, three-dimensional holographic images). The materials may be used as transparent media for inputting three-dimensional structures, for example comprising focussed coherent radiation (LASER) particularly as three-dimensional data storage media or for the three-dimensional representation of objects.
The material may conventionally be used in place of or in conjunction with glass up to service temperatures of 145xc2x0 C. Exterior applications for the transparent materials are roofing, window panes, films, glazing of glasshouses, in the form of twin-wall sheets for example. Further applications are covers to protect mechanically sensitive systems with high transparency at the same time, e.g. in the photovoltaics field, particularly solar cells or solar collectors. The plastics according to the invention may be coated with other materials, particularly with nanoparticles to increase scratch resistance, metals and other polymers.
Examples of domestic applications are transparent packing materials with low water permeability, household articles produced by extrusion or injection moulding, e.g. pots and containers. Also domestic appliances and transparent lampshades.
As temperature-resistant rigid foams the plastics may be used for insulation in the building and technology field (house and appliance insulation, for refrigerators for example) and replace polystyrene and polyurethane foam for example. The high long-term service temperature is an advantage.
Because of the low density (d less than 1) and weight-saving which results therefrom the materials are particularly suitable for applications in the motor vehicle, aviation and aerospace industry for instrument panels, transparent covers of instrument systems and of light sources, on-board glazing and insulating material.
The materials are insulators for electric current and are therefore suitable for producing capacitors (e.g. dielectrics), electronic circuits and equipment housings. Further applications in the electrical industry are based in particular on the combination of high optical transparency with high heat deflection temperature, low water absorption in conjunction with light from suitable emitting sources. The materials are therefore suitable for producing light-emitting diodes, laser diodes, matrices for organic, inorganic and polymeric electroluminescent materials, opto-electrical signal receiving equipment, data transmission systems by replacing glass fibre (e.g. polymer optical fibres), transparent materials for electronic display media (screens, displays, projection equipment) e.g. of liquid crystal substrates.
The materials are suitable for applications in medical technology for transparent extruded or injection moulded articles for sterile and non-sterile analytical vessels, Petri dishes, microfilter plates, microscope slides, hoses, breathing tubes, contact lenses, spectacle lenses and containers of infusion solutions or drug solutions for example, extruded and injection moulded articles for applications in contact with blood, particularly for producing syringes, cannulas, catheters, short and long-term implants (e.g. artificial lenses), flexible tubes for blood, membranes for blood detoxification, dialyzers, oxygenators, transparent plasters, stored blood containers and suture materials.